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Discussion Starter #1 (Edited)
So after replacing my (indeed broken) battery, I still find it empty after about 3 days of not using my car.
I've been to a garage to read out the ECU (and get the EKA :)) and there was no fault present in it's memory (how surprising :p). As I've searched through the forums, I found a list of possible causes which I'm looking at.

First off is the MEMS relay unit. I had a discussion with the guy at the garage and he told me he'd replace the main relay as that would be the cause of this in most cases. He also warned me that in 9 of 10 times, he'd break the case of the box while removing it because it's so fragile.

I've scraped a bit off of the plastic to make it easier to remove:


Next I put a flat and sharp screwdriver in from the top and wiggled it out, unbroken :D
I've opened the unit for inspection, there's a few bad solder pads there, some black contact points (I think the starter relay, which would make sense as it probably sparks). But no sticky contacts. All 4 relays were in rest position.. So either I switched the stuck relay when removing it, or it's the ECU that keeps one of the relays closed.
Here's what the board looks like now:


Note the bad solder pads


Note the blackened contact point

Next up is reflowing the solder and then I'll measure the voltages coming from the connectors when the car is off to see if the ECU keeps a relay closed.
 

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Mmmm....Rover..
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Two things....

Could you please resize the pictures attached to your post, it will make it easier for everyone to read.

The MFU and the MEMS relay module are two different items. You have opened the MEMS relay module, the MFU is fitted to the rear of the fusebox.

I would go with the engine ECU keeping the main relay energised as being as possible cause of your fault.

After the ignition is switched off the main relay should stay on for a maximum of two minutes... this will be easy to see with the MEMS relay module open.
 

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Discussion Starter #3 (Edited)
Resized, sorry.. I'd guessed the forum would do that :)

Ok.. now I'm confused.. :)
On the Rave CD, I found the schematics for my '96 416 (1995 export, is that the correct one?). Look at those, the 'charging and starting' schematic mentions the 'multi function relay unit'. The MEMS schematic mentions the 'mems relay module' Both have 4 relays, with the same numbers and the same connector numbers (157 / 154). Am I looking at the wrong schematics?

If you say the rear of the fusebox, is that the one inside or under the bonnet?

I'll test if the main relay (in the mems module, right?) will stay closed.

Thanks for your help!

PS: a quick picture under the bonnet:
 

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Discussion Starter #4
So.. it's indeed the main relay as you suggested. When I switch the contact to II and then off, I measure 0.5A current from the battery to the car. When I then disconnect the battery, the main relay switches off and the current falls back to 0.025A.

As you, and some other suggested, this is caused by the ECU. But what causes this? Is it soft- or hardware?
When in the garage, we verified that the ECU was up to date in firmware.
 

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Mmmm....Rover..
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It's a hardware fault, a component failure within the ECU.

0.4 to 0.6 amp current drain is the classic sign of the main relay being kept on.
 

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Discussion Starter #6
It's a hardware fault, a component failure within the ECU.

0.4 to 0.6 amp current drain is the classic sign of the main relay being kept on.
Hmm so one of the FET's that has died, or is it the uC? I'm quite comfortable with electronics, and I'd hate to send the ECU in to fix it for a lot of money if I could have done it myself ;o)
 
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